Light Emitting Diodes (LEDs) have many advantages over conventional light sources, such as incandescent, halogen and fluorescent lamps. These advantages include longer operating life, lower power consumption, and smaller size. Consequently, conventional light sources are increasingly being replaced with LEDs in traditional lighting applications. As an example, LEDs are currently being used in flashlights, camera flashes, traffic signal lights, automotive taillights and display devices.
One area of application for LEDs is in seven segment displays. A problem with currently available LED-based seven segment displays is height. Specifically, there are no seven segment displays available in the market today that have a product height of 3 mm or less. An example of a traditional LED segment 100 used in a seven segment display is depicted in FIG. 1. The LED segment 100 of the prior art traditionally includes a plastic housing 104 fastened to a Printed Circuit Board (PCB) substrate 108 via one or more housing seats.
The completed segment 100 also typically comprises a light source 120 located in a cavity of the housing 104, one or more bonding wires 124 connecting the light source 120 to an electrical lead on the PCB substrate 108, a protective encapsulant 128 that protects the light source 120 and bonding wires 124 from ambient moisture, and a conditioning encapsulant 132 that is used for conditioning light generated by the light source 120 before it exits the segment 100.
In some embodiments, the housing 104 of a segment 100 is fastened to the PCB substrate 108 via a first housing seat 112a and a second housing seat 112b. The housing seats 112a, 112b are usually formed by a process where pegs of the housing 104 are inserted through holes in the PCB substrate 104 and then the pegs are subjected to a combination of heat and pressure until the ends of the pegs mushroom outwardly (i.e., become larger in area than the holes of the PCB substrate 104) and secure the housing 104 to the PCB substrate 108.
This practice of establishing housing seats 112a, 112b to secure the housing 104 to the PCT substrate 108 is generally acceptable in the industry today. However, it can have drawbacks. In particular, the pressure and/or heat applied to the segment 100 to form the housing seats 112a, 112b places a limitation on the thickness of the housing 104 and PCB substrate 108. If the housing 104 or PCB substrate 108 are too thin (e.g., less than 3 mm collectively), then the pressure and/or heat may cause faults in the housing 104 or PCB substrate 108.
Another drawback to using the segment 100 construction depicted in FIG. 1 is that an air gap 116 is created between the housing 104 and PCB substrate 108 when the housing seats 112a, 112b are established. The air gap 116 is generally not very large, but does necessitate the protective encapsulant 128 to protect the light source 120. Without the protective encapsulant 128, ambient moisture would be allowed to reach the light source 120 via the air gap 116 and could potentially damage the light source 120.